In an unusual move‚ the five major broadcast and cable news networks have prepared a joint open letter that urges President Biden and former President Donald J. Trump to participate in televised debates ahead of Election Day‚ according to two people with direct knowledge of their plans.The letter endorsed by ABC‚ CBS‚ CNN‚ NBC and Fox News thrusts into public view a question that has swirled within media and political circles: whether the presidential debates‚ one of the nations last...